I've really only been watching fallon since they announced he was taking over for Leno - never been a huge late night guy. Then I found his show on Hulu+ and its been cracking me up ever since. This bit is definitely a highlight.
Look up his previous video with Bruce; he dresses up as Neil Young and sings Sexy and I Know It with him (dressed up as this springsteen, of course). There's also one of just Jimmy doing Whip My Hair.